Mediastinoscopy More Reliable Than PET for Characterizing Granulomatous Inflammation in Lymph Nodes

Crina Frincu-Mallos, PhD

October 20, 2008

October 20, 2008 (Baltimore, Maryland) — Granulomatous inflammation in mediastinal lymph nodes (MLN) that were either excised or biopsied at mediastinoscopy needs full characterization through microbial stains, even when it is initially diagnosed as sarcoidosis, a new study shows.

"We found that 70% of the patients had lung cancer associated with granulomatous inflammation," presenter Hanan Abdel Monem, MD, postdoctoral fellow at Baylor College of Medicine, in Houston, Texas, said in an interview with Medscape Pathology. Interestingly, "only some of them had lymphadenopathy," added Dr. Monem.

Mediastinoscopy-guided surgical resection or biopsy of MLN is needed to stage lung neoplasms and diagnose causes of lymphadenopathy.

"There are more and more people relying on PET [positron emission tomography] scans as a staging mechanism," lead author Linda K. Green, MD, professor of pathology at Michael E. DeBakey VA Medical Center and Baylor College of Medicine, told Medscape Pathology in an exclusive interview.

"Some of the patients with granulomatous disease will show PET-scan positivity and therefore they may be upstaged" (i.e., not be considered surgical candidates if their doctor relies on a PET scan), noted Dr. Green.

"We have found that mediastinoscopy in resectable lung tumor is still the gold standard, compared with PET scans, because of the very nature of the fact that malignancies can induce granulomatous disease in the mediastinum yet not be associated with metastases in the mediastinum," concluded Dr. Green.

The findings were reported here at the American Society for Clinical Pathology 2008 Annual Meeting.

The investigators sought to determine common and unusual causes of granulomatous inflammatory disease in the mediastinum.

They reviewed their files going back to 1992 and analyzed the clinical, radiography, histology, and culture data and the clinical course of 76 patients, 71 males and 5 females, ranging in age from 29 to 80 years.

A total of 38 patients had malignancies: 35 had lung cancer, 1 had melanoma, 1 had esophageal cancer, and 1 had renal cancer. Of these patients, the majority (n = 29) presented no MLN metastases. The rest of the patients had MLN with metastases (n = 6) or infections with Histoplasmosis (n = 1) or Cryptococcus (n = 2).

A total of 21 non-caseating granuloma inflammations were diagnosed as sarcoidosis. In addition, there were 13 primary infectious causes: 5 had tuberculosis, 4 had Histoplasma capsulatum, 2 had Mycobacterium avium intracellulare, 1 had Actinomyces, and 1 had Moraxcella.

"Necrotizing or caseating granulomatous inflammation is seen with infections, including mycobacteria and fungal infections, with or without a concurrent lung mass," the authors stated in their poster presentation.

Dr. Green pointed to the primary clinical importance of this study: "In the VA [Veterans Affairs], we have an older male population, and there are lots of concomitant infections, such as tuberculosis or histoplasmosis, which could be dormant but still show positive in a PET scan."

"This is the kind of study the general pathologist would like to see more of — very practical, and addressing a problem that we deal with almost every day," Daniel D. Mais, MD, FASCP, medical director of Hematopathology at St. Joseph's Mercy Hospital, in Ann Harbor, Michigan, told Medscape Pathology. Dr. Mais was not involved in the study.

"The issue is: How much do we need to work up these granulomas when we first find them in sample biopsies?" continued Dr. Mais. "There are differences between specialists' practices. Some will do all of the microbial stains every time they see a granuloma, others think that if it looks like a sarcoidal granuloma, there is no need for further characterization."

"This kind of study helps reinforce the need to do all the microbial stains," added Dr. Mais. "Often, if you give the patient a diagnosis of sarcoidosis, for example — which is the diagnosis you would give if you see a granuloma and you did not find any organisms — the patient may get steroids, and steroids are exactly the opposite of what people with these infections need," concluded Dr. Mais.

The study did not receive commercial support. Drs. Green, Monem, and Mais have disclosed no relevant financial relationships.

American Society for Clinical Pathology (ASCP) 2008 Annual Meeting: Poster 29. Presented October 17, 2008.

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